The invention relates to a slide key having a slide bar. The slide bar is displaceable between two axially spaced switch positions along an axis of displacement defined by a housing into which the slide bar fits. The slide bar is biased for displacement towards one of these positions by a spring. The slide bar has a surface which defines a somewhat heart-shaped hollow depression surrounding a projection. The projection has one rear surface facing away from and one front surface towards the spring. The housing has an interiorly located recess from which an inclined peg projects. The peg engages the rear surface of the projection to thereby lock the slide bar into a particular one of the switch positions.
Such a slide key is suitable for all switch arrangements actuable by means of a press button or key--arrangements from electrical push-button switches to fountain or ball point pens with retractable tips. There are a number of apparatuses in which a spring-biased slide bar is moved from one to another switch position by pressing the slide bar in the direction of the other position.
The locking element of the slide key consists exclusively of a cylindrical peg. This peg has two ends. One engages the projection and one passes through recess in the upper part of the housing and is therein connected to the housing. The one end projecting away from the housing is acted upon by a leaf spring. This leaf spring presses the peg against the bottom of the heart-shaped depression.
The heart-shaped hollow depression has an enclosed symmetric or asymmetric form and is so constructed that the peg is forced along the bottom of the depression always in a well-defined direction. The recess from which the peg projects is formed in such a manner that the peg can freely turn around in a plane perpendicular to the axis of displacement as the one end of the peg is passed along the bottom of the depression. When the slide bar is pressed against the spring and then released, the spring forces the slide bar away to a position in which the rear surface of the projection extending from the slide bar is engaged by the peg. This engagement locks the slide bar into a particular position. The peg is then jammed against the edges of the recess in the housing. The force of the locking is therefore transmitted from the projection of the hollow depression to the peg and from there to the edge of the recess of the housing.
The trend towards miniaturization means that the switch path of the electrical press key is constantly being shortened. The cross-section of the projection and the diameter of the peg must be reduced to provide a more compact instrument. Consequently, the interengaging parts of the locking mechanism must hold the slide bar in the locked position with a reduced cross-section of structure and material. But the present disadvantage of conventional slide keys is that either the materially weakened projection or the peg will be broken off because of the outwardly directed force of the spring--even when the springback force of the spring is reduced by a percentage corresponding to the reduction in size of the locking mechanism's interengaging parts. This problem is particularly critical with the so-called "piano key selectors" having master switches and keys with high operating forces.